StarDate Podcast

The roster of “dwarf planets” keeps growing. But it’s not official – there’s no league office to tell us who’s on the roster and who’s not. Various groups keep their own lists, but they don’t agree on which objects belong. The dwarf-planet category was formalized a couple of decades ago. Astronomers had discovered some new Pluto-like objects beyond the orbit of Neptune. They had to decide whether to add those objects to the roster of planets, or to put them in a new category. So in 2006, the International Astronomical Union voted to create the “dwarf planet” designation. A dwarf planet was defined as a body that’s large enough for its gravity to pull it into a rounded shape, but not large enough to clear its orbit of other bodies. The initial list included Pluto and three other distant objects, plus Ceres, the largest asteroid. Since then, astronomers have discovered thousands more objects in the realm of Pluto and beyond. Most of them are fairly small. But some are larger. Because they’re so far away, though, it can be tough to figure out an exact size and mass. So that makes it harder to decide whether some of these bodies are dwarf planets, or just big comets or asteroids. Today, most planetary scientists agree on a core list of about 10 dwarf planets. Another dozen or so are considered good candidates. And many more are possibilities – including a recently discovered one that we’ll talk about tomorrow. Script by Damond Benningfield

A bright star and planet team up with the Moon early tomorrow to form a tight, beautiful triangle. Pollux will stand close to the lower left of the Moon, with much brighter Jupiter about the same distance to the lower right of the Moon. Pollux is the brightest star of Gemini, while Jupiter is a planet. Jupiter is by far the giant of the solar system. It’s more than twice as massive as all the other planets combined. And it’s about 11 times the diameter of Earth. That makes it big enough to hold 1300 Earths. But a recent study says that Jupiter might have been much bigger during its infancy – about two or two-and-a-half times its current diameter. That would have made it big enough to hold thousands of Earths. Scientists came to that conclusion by studying the orbits of two of Jupiter’s small, close-in moons. The orbits are slightly tilted. Simulations showed that the moons were pushed into those orbits by the larger moon Io as it moved away from Jupiter. Those calculations revealed Jupiter’s original size and other details. Jupiter probably formed in just a few million years – much quicker than most of the other planets. By then, the supply of planet-making materials had dried up. So Jupiter’s gravity began squeezing it and making it spin faster. Eventually, the planet reached a point where it couldn’t shrink any farther – leaving the smaller but still-giant world we see today. Script by Damond Benningfield

A star that may be in a death spiral wants the universe to know about it. Every four and a half days it creates a burst of X-rays. The cause of those outbursts may be leading to the star’s demise. The possibly dying star is in a galaxy that’s about 300 million light-years away. During evening twilight now, that spot is quite low in the west, below the bright star Arcturus. According to a recent study, the story probably involves the star; a black hole, nicknamed Ansky, that’s a million times the mass of the Sun; and a wide disk of hot gas around the black hole. The star is following a tilted orbit around the black hole. Every few days, the star plunges through the disk. That heats the gas around the star, so gas blows away from the disk in bubbles that may be as massive as the planet Jupiter. Each passage robs the star of a bit of its orbital energy, so it spirals closer to the black hole. If the star is the mass of the Sun, it could last another five or six years before it dives into the black hole or is ripped apart by the black hole’s gravity. If the star is heavier, it could survive a little longer. Astronomers discovered the system in observations by two X-ray telescopes in space. They’ll use those same telescopes to watch the system in the years ahead. If the outbursts get more frequent, it’ll confirm they’re on the right track, and the star is on the wrong one – headed toward its destruction. Script by Damond Benningfield

There’s a season for everything, from football to Broadway to allergies. There are seasons in the heavens as well. And the next act in one of those seasons plays out early tomorrow: an occultation by the Moon of the star Elnath – the tip of one of the horns of Taurus. An occultation takes place when one object covers up another. The Moon occults a few fairly bright stars every month. And the occultations occur in seasons. That’s because the Moon’s orbit is tilted with respect to the ecliptic – the Sun’s path across the sky. The Moon moves back and forth across the ecliptic, allowing it to occult any star within a few degrees of that path. But its position relative to any particular star changes from year to year. As a result, occultations occur in bunches – in seasons. Now, the Moon is in the middle of its occultation season with Elnath. The season began in 2023, and continues into 2027. Because of the different angles to the Moon and star, and the short length of each event, only a few of the occultations are visible from a particular location. This occultation will be visible from the far-southwestern United States. Elnath and the Moon rise into good view after midnight, with the star to the lower left of the Moon. The Moon will slip toward Elnath as they climb higher. From most of the country, the Moon and star will just miss each other – a “seasonal” encounter in the dawn sky. Script by Damond Benningfield

The Milky Way is packed with star clusters – thousands of them. They contain anywhere from a few dozen stars to more than a million. And the most impressive of them all is right in the middle – it surrounds the supermassive black hole at the heart of the galaxy. The Nuclear Star Cluster contains up to 10 million stars. They extend a couple of dozen light-years from the black hole in every direction. But most of them are packed in close. If our part of the galaxy were that densely settled, we’d have a million stars closer to us than our current closest neighbor, Alpha Centauri. So any planets in the cluster would never see a dark night. Most of the stars in the cluster formed about 10 billion years ago, when the galaxy was young. But there was another wave of starbirth about three billion years ago, and a smaller one just a hundred million years ago. Each wave might have been triggered when the Milky Way swallowed a smaller galaxy. As the galaxies merged, clouds of gas and dust settled in the middle, around the Milky Way’s black hole. That gave birth to new stars – populating the galaxy’s most impressive cluster. The cluster is in Sagittarius, which is due south at nightfall. The constellation looks like a teapot. The center of the galaxy is in the “steam” rising from the spout. But giant clouds of dust absorb the light from the galaxy’s heart, so it takes special instruments to see the cluster. Script by Damond Benningfield

Guillaume Le Gentil spent more than 11 years away from his native France just to witness two brief astronomical events. Along the way, he had to survive war, a hurricane, disease, and grumpy officials. When he got home, he’d lost his job and been declared dead. But the real hardship? He missed both events. Le Gentil was born 300 years ago this week. He studied theology, but decided on astronomy as a career. He became a member of the Royal Academy of Science at age 28. Le Gentil and other astronomers hoped to measure a 1761 transit of Venus across the Sun from many locations on Earth. The details would reveal the Sun’s distance – the basic “yardstick” for the entire solar system. Le Gentil planned to watch from India. He headed out in March of 1760. War with England complicated the trip, and his ship was blown off course. On the day of the transit he was still at sea, where it was impossible to make observations. The next transit was just eight years away, so Le Gentil decided to hang around. He planned to watch from the Philippines. But he got a chilly reception, so he returned to India. He set up an observatory and waited. But the day of the transit was cloudy – until shortly after it was over. Heartbroken, Le Gentil headed home. It took two hard years to get there – only to encounter even more problems. But he worked things out, and published two volumes about his travels in the name of science. Script by Damond Benningfield

If you’d like to travel into the future – even the far-distant future – you don’t need a time machine. Instead, a starship will do just fine. Fire up the engines, head into space, and keep your foot on the gas. The laws of physics seem to make it impossible – or nearly so – to travel through time in anything like the modern concept of a time machine – something that allows you to move through the centuries at will. Yet those same laws make it possible to zoom into the future. The concept is known as time dilation. As you travel faster, your clock ticks more slowly compared to the clocks of those you left behind. It’s been proven by putting atomic clocks in airplanes and aboard GPS satellites. In fact, if GPS clocks weren’t adjusted to account for it, the entire system would fail. At the speed of a satellite, the difference is tiny – a few millionths of a second per day. As speed increases, though, the effect becomes more significant. If you could travel at 90 percent of the speed of light for one year as measured by the clock on your ship, more than two-and-a-quarter years would pass back on Earth. At 99 percent of lightspeed, it’s more than seven years per ship year. And at 99.99 percent, the ratio is 70 Earth years per ship year. Of course, there is the problem of finding a fast starship to carry you. But so far, that’s the only known way to beat Time – and travel into the future. Script by Damond Benningfield

Based on the number of books, movies, and TV shows about it, you might assume that traveling through time is almost as easy as ambling through the park on a sunny day: Just build a TARDIS or soup up your Delorean, and off you go. Alas, the arrow of time moves in only one direction. It allows you to travel into the future, but roadblocks seem to prevent any method that scientists can envision for traveling in the other direction. Wormholes, for example, are theoretical “tunnels” through space and time. They seem to allow travel to other times – past or future. But there’s a problem: The wormhole may collapse as soon as anything enters it – a person, a spaceship, or even a radio beam. Another possibility for traveling into the past is moving really fast. Albert Einstein’s theories of relativity suggest that anything moving faster than light might move backward in time. But any physical object moving at lightspeed would become infinitely massive. That means you’d need an infinite amount of energy just to reach lightspeed – and even more to go faster. A few decades ago, Stephen Hawking suggested that the universe doesn’t like time travel. He wrote that the laws of physics may stop anyone from ever building a time machine – keeping the past safe from its own future. Even so, physics provides some tricks that allow travel to the future, and we’ll have more about that tomorrow. Script by Damond Benningfield

If a cosmic giant sat on a big, gassy planet, it would look a lot like Saturn, the second-largest planet in the solar system. It’s 10 percent wider through its equator than through the poles. But Saturn flattened itself – a result of its low density and fast rotation. Saturn consists of a series of layers. Its core is a dense ball of metal and rock. Around that is a layer of hydrogen that’s squeezed so tightly that it forms a metal. Around that is a layer of liquid hydrogen – the lightest and simplest chemical element. And the planet is topped by an atmosphere that contains methane, ammonia, water, and other compounds. Despite its great size, Saturn spins once every 10.7 hours. That pushes material outward, making the planet fatter through the equator. The combination of its composition and rotation makes Saturn especially light – it’s less dense than water. Saturn doesn’t have a solid surface. But scientists have defined a “surface” as the depth in its atmosphere where the pressure equals the surface pressure on Earth. At that level, Saturn’s gravity is only a bit stronger than Earth’s gravity. So if you were floating at that altitude, you’d feel like you’d added a few pounds. And because of Saturn’s flattened shape, you’d feel heavier at the poles than the equator. Look for Saturn near the Moon tonight. It looks like a bright star to the right of the Moon in early evening, and farther below the Moon at dawn. Script by Damond Benningfield

Building the planets of the solar system was like building a city – it didn’t happen all at once. Instead, it probably took a hundred million years or more to complete the construction project. The first to be completed were Jupiter and Saturn, the Sun’s largest planets. They came together in the prime real estate for planet building – the region with the most raw materials. Closer to the Sun, it was so hot that ices were vaporized and blown away. Farther from the Sun, the material thinned out. But at the distance of Jupiter and Saturn, the balance was just right. The two giants took shape in a hurry. Small grains of ice and rock stuck together to make pebbles, then baseball-sized chunks, then boulders, and so on. That quickly built massive cores, which then swept up huge amounts of leftover hydrogen and helium gas. So within just a few million years, Jupiter and Saturn have grown to monstrous proportions. Uranus and Neptune took shape a little later – within tens of millions of years. Earth and the other rocky inner planets took a bit longer – at least a hundred million years. So the biggest planets of the solar system are also the oldest – dating to shortly after the birth of the Sun. Saturn stands close to the Moon the next couple of nights. The planet looks like a bright star. It’s to the lower left of the Moon as darkness falls tonight, and about the same distance to the right of the Moon tomorrow night. Script by Damond Benningfield

The 41st episode of a celestial series plays out tomorrow: a total lunar eclipse. It’ll be visible around much of the world – but not the Americas. Every eclipse belongs to a series, called a Saros. The eclipses in a Saros are separated by 18 years plus 11 and a third days. If we could watch all the eclipses in the cycle play out, we’d see the Moon pass through Earth’s shadow from top to bottom or bottom to top. So the Moon barely dips its toe in the shadow at the beginning and end of the sequence. But it’s fully immersed during the middle of the cycle, creating total eclipses. And because of that extra third of a day in the cycle, each eclipse occurs a third of the way around the world from the previous one. This eclipse is part of Saros 128. The cycle began in 1304 and will end in 2566 – 71 eclipses in all. Most of Asia and Australia will see this entire eclipse, from beginning to end. And most of the rest of the world will see at least part of it. Totality – when the Moon is completely immersed in the shadow – will last for an hour and 22 minutes. But the eclipse occurs during the middle of the day for those of us in the United States, so we won’t see any of it. What we will see the next couple of nights, though, is a beautiful full Moon – the Fruit Moon or Green Corn Moon – completely free of Earth’s dark shadow. Script by Damond Benningfield

The Moon will briefly cover up the tail of the sea-goat tonight – Deneb Algedi, the brightest star of Capricornus. The sequence will be visible across much of the United States. This vanishing act is an occultation – a type of eclipse in which one object completely covers another. But eclipses are nothing new for Deneb Algedi. Not only does it periodically get covered up by the Moon, but it stages its own eclipses – two of them every day. What we see as Deneb Algedi is a binary – two stars in a tight orbit around each other. The main star in the system is about twice as big and heavy as the Sun, and much brighter. Its companion is a little smaller and fainter than the Sun. We’re looking at the system edge-on, so the stars pass in front of each other – creating eclipses. When the fainter star crosses in front of the brighter one, the system’s overall brightness drops by about 20 percent – enough for a skilled skywatcher to notice. But when the brighter star eclipses the fainter one, the dip is much smaller, so it’s detectable mainly with instruments. The stars orbit each other once a day. That means we see two eclipses per day – just 12 hours apart. Deneb Algedi isn’t especially bright, so it’s hard to see through the bright moonlight. But binoculars will help you pick it out. From much of the western U.S., the Moon will just miss the eclipse-happy tail of the sea-goat. Script by Damond Benningfield

The planet Jupiter will slide past one of the brighter stars of Gemini the next few mornings. At their closest, they’ll be separated by just a fraction of a degree. The star is Wasat – from an Arabic phrase that means “the middle.” But the middle of what has been lost over the centuries. The star also is known as Delta Geminorum – its Bayer designation. The system was devised in the early 17th century by German astronomer Johann Bayer. He named all of the stars in the constellations that were visible from the northern hemisphere. Each star was given a Greek letter followed by the constellation name. If he ran out of letters, he switched to the Latin alphabet. In most constellations, Bayer named the stars in the order of their brightness. The brightest was alpha, the next-brightest was beta, and so on. Sometimes, he ranked the stars on their location or some other system. And he named the stars based on how they looked to the naked eye, so the rankings were completely subjective. So even though delta is the fourth letter in the Greek alphabet, Delta Geminorum is only the eighth-brightest star in Gemini. Jupiter and Wasat are well up in the east at dawn. Jupiter looks like a brilliant star, far to the upper right of even-brighter Venus. Wasat will stand below Jupiter tomorrow. Jupiter will drop past it over the following couple of days, so they’ll be at their closest on Saturday and Sunday. Script by Damond Benningfield

Water is the key ingredient for life on Earth. And as far as we know, it’s a key ingredient for life everywhere else in the universe as well. That shouldn’t be a problem, though, because there’s plenty of water to go around. Water is common in part because it’s made of two of the three most common elements in the universe – hydrogen and oxygen. They come together in the cold of deep space to make grains of ice. Some of those grains are found in the clouds of gas and dust that give birth to new stars and planets. Others form inside those clouds. In recent years, astronomers have found evidence of water in other star systems, and even in other galaxies. They’ve found grains of ice in the disks of material around newborn stars. They’ve seen giant belts of comets, which contain a lot of ice. They’ve discovered water vapor in the atmospheres of a few planets. And they’ve even found evidence that some planets could be covered in oceans of liquid water. One example is TOI 1452 b, which orbits a star that’s much smaller and fainter than the Sun. The planet itself is bigger and heavier than Earth. Given its details and its distance from the star, scientists say it could have a deep global ocean – a possible home for life. TOI 1452 is about a hundred light-years away, in Draco. The dragon twists high across the north at nightfall. But the star is much too faint to see without a telescope. Script by Damond Benningfield

Earth is the only body in the solar system with liquid water on its surface. But it’s not the only one where you can find water. In fact, water is everywhere – from comets and asteroids to the giant planets. Comets and asteroids are chunks of rock, metal, and ices – including water ice. Comets have more ice, but most asteroids probably have large amounts as well. Such bodies might have supplied much of the water on Earth when they collided with our planet billions of years ago. Water ice is common throughout the solar system. It’s been seen at the poles of the Moon and the planet Mercury – the Sun’s closest planet. It forms large polar caps on Mars. And it coats many of the moons of the giant outer planets. Water also has been detected in the clouds of Jupiter and Saturn. And it may be a major component of the outer layers of Uranus and Neptune, the Sun’s most remote planets. To find liquid water, you have to go deep. There may be global oceans of water far below the surfaces of some of the big moons of Jupiter and Saturn, and perhaps some moons of Uranus and Neptune as well. Some of those oceans could hold more water than all of Earth’s oceans combined. On Earth, water is a key ingredient for life. So some of the moons of the outer planets are considered good places to look for life – swimming in oceans of liquid water. We’ll talk about water beyond the solar system tomorrow. Script by Damond Benningfield

Water is all about extremes. The atoms that make up water molecules were forged in some of the hottest environments in the universe. But most of the molecules formed in the cold of deep space. A water molecule consists of two hydrogen atoms plus one oxygen atom – H-2-O. A hydrogen atom contains one electron and one proton. The electrons formed in the first fraction of a second after the Big Bang, when the universe was extremely hot and dense. The protons formed a few minutes later. By about 380,000 years, the universe had expanded and cooled enough for the electrons and protons to stick together to form atoms. And today, hydrogen accounts for more than 90 percent of all the atoms in the universe. Hydrogen and helium, the other major element forged in the Big Bang, soon came together to make stars. And a star’s core is hot enough to “fuse” lighter elements to create heavier ones. The first steps in that process create carbon, nitrogen, and especially oxygen – the third-most abundant element in the universe. When stars die, they expel some of those elements into space. And in the cold away from the stars, hydrogen and oxygen can stick together to make molecules of water. Some of the water’s incorporated into planets – including our own. So the next time you take a cool drink of water, think of the hot-and-cold origins of this important compound. We’ll have more about water tomorrow. Script by Damond Benningfield

To have a strong heart, you naturally need strong arteries. And that’s not a problem for Antares, the heart of the scorpion. It’s flanked by two fairly bright stars that historically have shared a name: Alniyat – an Arabic name that means “the arteries.” The stars probably are siblings of Antares. They all formed from the same giant complex of gas and dust, within the past 10 million years or so. Alniyat I is also known as Sigma Scorpii. It’s a system of four stars. Two of them form a tight pair, with a third close by. The fourth star is farther out. Both stars in the tight grouping are much like Antares. They’re many times the mass of the Sun, so they’ll probably end their lives with titanic explosions. Antares is a little farther along its lifecycle, so it’s closer to that showy demise. Alniyat II is Tau Scorpii. It’s a single star. It, too, is destined to explode as a supernova, but not for several million years – a little later than Antares and the main star of Sigma. On the astronomical clock, though, that’s close – just a few ticks away. Antares and its arteries are close to the right of the Moon at nightfall this evening. Sigma is close to the right or upper right of Antares. Tau is about the same distance to the lower left of Antares. The arteries aren’t as bright as the scorpion’s heart, though, so you might need binoculars to see them through the glare. Script by Damond Benningfield

A spacecraft that’s on it way to Jupiter is “pinballing” around the solar system, getting an extra “kick” as it zips close to the planets. It’ll get the next kick tomorrow, from Venus. The spacecraft is JUICE – Jupiter Icy Moons Explorer. It’s scheduled to arrive at Jupiter in 2031. But it needs help to get there. And it gets that help from the gravity of Venus, Earth, and the Moon. During each encounter, the craft “steals” a bit of gravitational energy. That speeds it up and sculpts its path around the Sun. The encounters drastically reduce the amount of fuel JUICE must carry, cutting its size and weight and reducing its cost. JUICE flew past Earth and the Moon a year ago. It’ll get additional boosts from Earth in 2026 and ’29. JUICE will scan Venus as it flies past. That will give scientists some extra information about the planet. And it’ll give engineers a chance to check out the craft’s instruments. When JUICE arrives at Jupiter, it’ll orbit the planet for almost three years. After that, it’ll begin orbiting the planet’s largest moon, Ganymede. Its observations of Ganymede and Jupiter’s other icy moons will reveal details about their possible buried oceans, which could be habitats for microscopic life. Venus and Jupiter are in the dawn sky now. Venus is the brilliant “morning star,” with slightly fainter Jupiter to its upper right – two destinations for a “pinballing” explorer. Script by Damond Benningfield

Only a few of the thousands of known planets in other star systems have ever been seen. Most exoplanets are discovered through their effects on their parent stars. But a system in Pegasus is a major exception. Astronomers have discovered four planets in the system – and they’ve seen all of them. HR 8799 is about 130 light-years from Earth. The star is bigger, brighter, and heavier than the Sun. And it’s much younger – tens of millions of years, versus four and a half billion years for the Sun. And that’s one reason we can see the planets – they’re still warm from their birth, so they produce a lot of infrared light. Another reason we can see the planets is that they’re a long way out from the star – many times the distance from Earth to the Sun – so they’re not masked by the star’s light. And the planets are giants – they’re up to 10 times the mass of Jupiter, the giant of our own solar system. Recent observations by Webb Space Telescope suggest the planets formed in the same way as Jupiter. Blobs of rock and metal stuck together to form a heavy core. The gravity of the core then swept up huge amounts of gas. The system might still be taking shape. A giant disk of dust surrounds the planets, and is being stirred up by their gravity. And the planets themselves may be shifting position – finding the right arrangement before this young, busy system settles down. Script by Damond Benningfield

A recently discovered planet is facing its final days. It’s evaporating, leaving a trail of debris that stretches halfway along its orbit. The planet is known by a catalog number – BD +05 4868 Ab. It’s only the fourth evaporating planet ever seen. It orbits the main star in a binary system in Pegasus, which is in the eastern sky at nightfall. The star is smaller and fainter than the Sun, and more than twice the age of the Sun. The planet was discovered by TESS, a planet-hunting space telescope. The planet passes in front of its parent star once every 30.5-hour orbit, blocking some of the star’s light. But the dips in starlight are ragged and look different from orbit to orbit. That suggests the planet is shedding material, forming a lumpy trail. The planet is small, and it orbits the star at just two percent of the distance from Earth to the Sun. At that range, it’s heated to 3,000 degrees Fahrenheit. That vaporizes minerals at the surface. The vapor boils into space, where it cools and condenses to form solid grains. That creates a thick trail that extends both behind and ahead of the planet. As more of the planet vaporizes, its gravity weakens, allowing even more material to escape. So the planet could vanish entirely in as little as a million years. Astronomers will look at the system with Webb Space Telescope – revealing more details about this vanishing planet. Script by Damond Benningfield

The Sun isn’t bothered by much. That’s because it travels through the Milky Way on its own. But most of the stars in the galaxy have at least one companion star. And the interactions between them can have a big impact. Consider Spica, a bright star near the Moon tonight. Although it looks like a single star, it’s really at least two stars. One of them is more than 11 times the mass of the Sun, while the other is about seven times the Sun’s mass. That makes Spica one of the more impressive binary systems around. The stars are extremely close together. They follow a stretched-out orbit that brings their surfaces to within about 10 million miles of each other. So the stars have big effects on each other. For one thing, their mutual gravitational pull distorts both stars. They’re shaped like eggs, with the tapered end pointing toward the other star. Also, the pull of the smaller star appears to create ripples in the larger one. And the tapered end of each star is hotter than its opposite hemisphere. In a few million years, the larger star will explode as a supernova. That’s likely to blast away some of the gas at the surface of the companion. And it’ll probably send the smaller star zipping across the galaxy – fired into space by a close companion. Look for Spica to the right of the Moon early this evening. The fainter planet Mars is farther to the lower right of the Moon. Script by Damond Benningfield

Mars is dry, cold, and quiet. But that hasn’t always been the case. Billions of years ago it was much busier – and perhaps a comfortable home for life. Mars has had three major geological ages. The oldest was the Noachian. It’s named for a large highlands region in the southern hemisphere. It began about 4.1 billion years ago, and lasted for 400 million years. The solar system was still packed with big “leftovers” from the birth of the planets then. Many of them slammed into Mars, forming wide basins that are still visible today. At the same time, giant volcanoes belched gases into the atmosphere. That trapped heat, making Mars much warmer. Clouds might have produced rain or snow. The precipitation carved rivers and filled lakes and maybe even a large ocean. Conditions could have allowed the formation of microscopic life. At the end of that period, there were fewer impacts and less volcanic activity. Mars cooled off, and the water dried up. So Mars became quieter as the Noachian Age ended, and the next age began. Mars is close to the right or upper right of the Moon early this evening. It looks like a fairly bright star. But it’s quite low in the sky, especially as seen from the northern half of the country, so you need a clear horizon to spot it. The star Spica, which is about twice as bright as Mars, stands to the upper left of the Moon. We’ll have more about Spica tomorrow. Script by Damond Benningfield

Every pilot knows to check the weather before takeoff – no one wants to fly into a storm. And in the future, they might want to check the space weather as well. Storms on the Sun can interfere with technology here on Earth – including aviation technology. Solar storms are giant explosions of energy and charged particles. When these outbursts hit Earth, the effects can range from damaged satellites to power blackouts on the ground. Some radio frequencies can be blacked out as well. Scientists recently looked at the impacts on aviation. They studied tracking information for three small aircraft recorded during a massive solar flare in February of 2024. The aircraft automatically reported their position and other details to air traffic control and to other aircraft. The position information came from GPS satellites. But several times during the solar storm, the aircraft briefly lost touch, or they received bad position information. The problems were brief. But future storms could cause bigger problems. Bad information from GPS satellites, drops in radio links, and even radar blackouts could force flight controllers to rely on older methods to keep planes and passengers safe. That could cause delays and backups – or worse. So the researchers suggested that space weather briefings be developed for pilots – helping them safely navigate through space weather. Script by Damond Benningfield

As Earth was thawing out at the end of the last ice age, it was hit by a powerful blast from the Sun. The storm would have triggered spectacular displays of the northern and southern lights. And it left an imprint in tree rings. Using that imprint, scientists have found that the storm was the most powerful yet recorded. And they even have a time for the event: the first quarter of the year 12,350 BC. Solar storms pelt Earth all the time. Most of the storms are small. But big ones can damage or destroy satellites, zap power systems on the ground, and cause other mischief. The biggest one ever seen took place in 1859. It knocked out telegraph systems around the world. But scientists have found evidence of even bigger events in the more-distant past. Some of the events are recorded in tree rings. Charged particles from the storms interact with Earth’s atmosphere to produce a radioactive form of carbon. Trees take up some of the carbon, which decays to a more stable form at a known rate. So comparing the ratio of carbon isotopes in tree rings can tell us when big storms took place. Researchers measured the carbon in rings from the end of the ice age. And they developed a new model of chemistry of the atmosphere during such cold periods. Their work showed that Earth was hit by the strongest solar storm yet discovered more than 14,000 years ago. More about space weather tomorrow. Script by Damond Benningfield

If you watch the stars on a dark night, it’s easy to think of the sky as a great dome. But as the night goes on, the dome rotates. New stars rise in the east, while others disappear in the west. So ancient skywatchers thought of the sky not as a dome, but a sphere that completely encircles us – the celestial sphere. To the Greeks, the sphere was real – a perfect crystalline surface, with the stars hanging from it like lanterns. Earth stood still at the middle of the sphere, which turned around it. Today, of course, we know that Earth is turning, and the stars are so far away that they appear to be fixed in place. Yet astronomers still use the celestial sphere. Their coordinate system is based on it. The system has lines of latitude and longitude, an equator, and north and south poles – all of which are projections of Earth’s coordinates. The celestial poles, for example, are based on the projection of Earth’s poles – the directions in which our planet’s axis is pointing. There’s also a celestial equator – an extension of Earth’s equator. As darkness falls tonight, it arcs from Aquarius, in the east; through Aquila, in the south; and down to Virgo, in the west. Only those who live near the equator can see the entire celestial sphere. For everyone else, it’s clipped. And at the poles, only half of the sphere is ever visible – a great dome showing the same stars all year long. Script by Damond Benningfield

Many “open” star clusters arch high overhead on summer nights. They’re lined up along the glowing band of the Milky Way – the outline of our home galaxy. Each cluster is a family of stars – from a few dozen to a thousand or more. But open clusters don’t stay together for long. Their stars eventually spread out, so the cluster disappears. Some families begin to spread out early – before many of their stars are even fully formed. One recently discovered example is called Ophion. It consists of more than a thousand stars. Astronomers found the group by analyzing data from Gaia, a space telescope. They looked through observations of more than 200 million stars. Then they narrowed their search to stars that are cooler than the Sun, and no more than 20 million years old. And Ophion just popped out. The stars form a giant clump that’s centered about 650 light-years away. But all of its members are going their own way. So they don’t form an obvious “cluster” – a tight grouping that’s easy to pick out. Ophion is on the edge of a region that’s given birth to many thousands of stars. Exploding stars in that region – or within Ophion itself – might have scattered the stars like bowling pins, keeping the family from sticking together. Ophion is near the middle of Ophiuchus, which is well up in the south-southwest at nightfall. You can see many clusters there – but not a hint of the ill-fated Ophion. Script by Damond Benningfield

Human eyes are perfectly tuned to see sunlight. But that’s a thin slice of the total range of light. As a result, we miss a lot of what’s out there – even objects that are big and close. A recently discovered example is a cloud of gas and dust that’s been named Eos. It spans about 40 times the width of the Moon. But it’s thinly spread, and it produces most of its light in the far-ultraviolet – wavelengths we can’t see. And even if we could see them, Earth’s atmosphere blocks them. So Eos wasn’t discovered until astronomers combed through observations made two decades ago by a Korean space telescope. The cloud’s inner edge is about 300 light-years away. It’s along the rim of the Local Bubble – a giant void around the solar system that’s been cleared out by exploding stars. Eos is about 170 light-years across. It contains enough gas to make more than 5,000 stars as heavy as the Sun. But there’s no evidence that it’s ever given birth to any stars at all. And while it could spawn stars in the future, that’s not likely. The cloud is evaporating, and should vanish in about six million years. Eos is centered along the border between the northern crown and the head of the serpent. That point is high in the west-southwest at nightfall, to the upper left of the bright star Arcturus. But unless you have your own space telescope, there’s no way to see this giant neighbor. Script by Damond Benningfield

Many centuries ago, people knew of only seven metals. That also was the number of known “planets” – the five true planets that are visible to the naked eye, plus the Sun and Moon. So each metal was associated with a planet – gold with the Sun, silver with the Moon, for example. Another metal with a good match was quicksilver. It’s the only metal that’s liquid at everyday temperatures, so it was associated with the quickest planet: Mercury. And it was even given the planet’s name. The planet moves back and forth between the morning and evening sky every few months. That quick motion is where the planet got its name. Mercury was the Roman messenger god, who flitted across the heavens on winged heels. The only spacecraft to study the planet from orbit didn’t find any trace of the metal mercury on its surface. And if there’s any of it near the planet’s equator, it would go through all three everyday phases of matter. At night, the planet is so cold that the metal would be frozen solid. At noon, it’s so hot that it would vaporize, forming a gas. And for much of the rest of the daytime, it would be a liquid – quicksilver puddles on a quicksilver planet. Mercury will stand close to the Moon during the dawn twilight tomorrow. It looks like a fairly bright star, to the lower right of the Moon. The brighter planets Venus and Jupiter align to their upper right – the planets of copper and tin. Script by Damond Benningfield

Early risers are in for a treat tomorrow. Venus, Jupiter, and the twins of Gemini congregate around the Moon. The group climbs into good view a couple of hours before dawn. Venus is close to the lower right of the Moon, Jupiter is farther to the upper right, and Gemini’s twins are to the upper left of the Moon. The brighter twin, Pollux, is especially close to our satellite world. Venus is the “morning star” – the brightest member of the group after the Moon. It shines so brightly because it’s close to Earth and the Sun, and because it’s topped by clouds of sulfuric acid. They reflect about three-quarters of the sunlight that strikes them. Jupiter is the next brightest – mainly because it’s the largest planet in the solar system. It’s about 11 times the diameter of Earth, and it’s more than twice as massive as all the other planets and moons put together. And Earth is moving closer to Jupiter now, so the planet will grow even brighter over the next few months. Pollux and Castor, the twins, are true stars. But they’re hundreds of thousands of times farther than the planets, which dulls their countenance. Even so, they’re easy to see through the moonlight – part of a beautiful panorama in the early morning sky. Another bright light rises well below the group: Mercury, the Sun’s closest planet. The Moon will stand close to it on Thursday, and we’ll talk about that tomorrow. Script by Damond Benningfield

The crescent Moon will slide past three bright planets over the next three mornings, growing thinner as it does so. First up is Jupiter, the largest planet in the solar system. It looks like a bright star below the Moon at dawn tomorrow. The Moon is in the part of its orbit that carries it between Earth and the Sun. It’ll reach that point on Friday night. As it drops toward the Sun, the Earth-Moon-Sun angle changes. So the Sun lights up less and less of the lunar hemisphere that faces our way. As a result, the crescent gets thinner day by day. Tomorrow, for example, about 15 percent of the lunar disk will be in the sunlight. By Wednesday, as it poses near Venus, it’ll be down to eight percent. And by Thursday, when it’s close to Mercury, it’ll be the barest of fingernails – it’ll be daylight across only about three percent of the visible disk. On the other hand, as the crescent gets smaller, the dark portion of the Moon will get brighter. That’s because that part of the Moon is bathed in earthshine – sunlight reflected from our own planet. As the Moon gets thinner and thinner in our sky, Earth will get fatter and fatter in the lunar sky, so earthshine will get brighter. It’ll reach its peak when Earth is full – at the same moment that the Moon is new. The Moon will be lost in the Sun’s glare then, but it will return to view a couple of days later – as a thin crescent in the evening sky. Script by Damond Benningfield

For a few weeks in the spring of 1764, Charles Messier was a star-cluster-discovering machine. He found five globular clusters in Ophiuchus, the serpent bearer. He cataloged them as Messier 9, 10, 12, 14, and 19. Messier wasn’t interested in the clusters – or even in the stars. Instead, he was looking for comets. At the time, finding a comet was a way to fame and fortune. Kings offered prizes to those who found comets. And comets were named for their discoverers – a bit of immortality. But Messier and others kept coming across fuzzy objects that resembled comets. Figuring out if they really were comets wasted time. So the French astronomer decided to compile a catalog of these distractions. He logged more than a hundred objects. They included star clusters, galaxies, stellar nurseries, and the final gasps of dying stars. Today, Messier’s list is the most famous of all astronomical catalogs. The globular clusters all look about the same. They’re tight balls of stars. Today, we know that the typical globular contains a hundred thousand stars or more. And they’re among the oldest residents of the Milky Way – more than 10 billion years old. Ophiuchus is a large constellation that stands well up in the southern sky at nightfall. Messier’s globulars are scattered across it. They’re all visible through binoculars – just don’t mistake them for comets. Script by Damond Benningfield

Barnard 68 is one of the darkest objects in our section of the galaxy. It’s a small cloud that absorbs the light of the stars behind it, so it looks like a dark “hole” in the Milky Way. Before long, though, that void may shine with the warmth of newly forming stars. Barnard 68 is a Bok globule – a small, dark sphere of gas and dust. It’s about 500 light-years away, half a light-year wide, and about three times the mass of the Sun. It’s part of a complex of dark clouds that stands in front of the glowing band of the Milky Way. Barnard 68 is so dark because it’s quite cold – temperatures at its center are close to absolute zero. But that may be about to change. The globule has been stable for millions of years. But there’s evidence that it’s recently been hit by a cosmic “bullet” – a smaller clump of gas and dust. That appears to be causing Barnard 68 to collapse. As it collapses, the cloud will get denser and hotter, and perhaps split into several smaller clumps. Within a few hundred thousand years, the clumps could be well on their way to becoming new stars – glowing balls of gas born from a dark “hole” in the Milky Way. Barnard 68 is in Ophiuchus, the serpent bearer, which is in the southern sky at nightfall. The Milky Way runs through a corner of the constellation. Several clouds darken the Milky Way – birthplaces of future stars. Script by Damond Benningfield

The gods of ancient Greece had complicated relationships. As an example, consider Ophiuchus. He’s represented by a constellation that passes across the southern sky on summer evenings. The constellation represented Asclepius, the god of medicine and the son of the god Apollo. In one version of the story, Asclepius killed a snake with his staff. But another snake dropped some herbs on the dead one, bringing it back to life. Asclepius then used those herbs to resurrect the son of King Minos. Business was so good for Asclepius that fewer people were entering the underworld. So Hades, the god of the underworld, complained to Zeus, the king of the gods. Zeus then killed Asclepius with a lightning bolt. But that didn’t sit well with Apollo. To appease him, Zeus placed Asclepius in the sky. Today, those stars are known as Ophiuchus, the serpent bearer. He’s depicted with a snake wrapped around his waist. And that’s why the symbol for modern medicine is a pair of snakes wrapped around a staff – it represents the story of Ophiuchus. Look for the serpent bearer high in the south as night falls. Its stars are faint. Under a dark sky, though, they form a pattern that resembles a coffee urn. It stands upright in early evening, but lies on its side later on. The constellation’s brightest star is at the top of the coffee pot – the “head of the serpent bearer.” More about Ophiuchus tomorrow. Script by Damond Benningfield

Earth has something in common with Titan, the largest moon of Saturn. They’re the only two bodies in the solar system with liquids flowing and ponding on the surface. In the case of Earth, that liquid is water. But on frigid Titan, it’s liquid hydrocarbons – methane and ethane. Titan is the second-largest moon in the solar system – a bit bigger than the planet Mercury. Its surface is extremely cold – hundreds of degrees below zero. Its atmosphere is thicker than Earth’s, and it’s topped by a dense layer of smog. The Cassini spacecraft used radar to peer through the clouds. And its findings were remarkable. It discovered rivers flowing across the surface, emptying into lakes and seas. It also found clouds, which occasionally produce rain. Everything we can see on Titan contains a lot of carbon-based compounds – some of the raw building blocks of life. That’s led to speculation that Titan might have the precursors to life – or even life itself – hidden in a giant ocean below the crust. To be clear, there’s no evidence of life. But future missions to Titan will sniff around for such evidence – perhaps adding to the list of things that Earth and Titan have in common. Saturn appears quite close to our own moon tonight. It looks like a bright star to the lower left of the Moon as they climb into good view, by about 11 o’clock. But you’ll need a small telescope to pick out Titan. Script by Damond Benningfield

One of the best-known meteor showers will be at its best the next couple of nights. Unfortunately, the gibbous Moon will be in the sky during the best hours for meteor watching. That will spoil the view of all but the brightest meteors. Perseid meteors are spawned by Comet Swift-Tuttle. The comet orbits the Sun once every 133 years or so. As it plies the interplanetary space lanes, it sheds tiny bits of rock and dust. The grains spread along the comet’s path. Earth flies through this path every August. The particles ram into the atmosphere at more than 130,000 miles per hour. They heat the air in front of them to thousands of degrees, forming the glowing streaks known as “shooting stars.” Swift-Tuttle is an especially big comet – about 16 miles in diameter. And its orbit sometimes brings it close to Earth. In August of 2126, for example, it’ll pass just 14 million miles away. And about 900 years later, it’ll miss by just one million miles. It’s hard to project the comet’s orbit more than a few thousand years into the future. So it’s possible that it could someday hit Earth – a collision that would wipe out most of the life on our fragile planet. Perseid meteors are best seen between midnight and dawn. Find a safe viewing site away from city lights, block out the Moon as much as you can, and scan the sky for the celestial fireworks. Script by Damond Benningfield

Social media may go wild the next few days – filled with reports of UFOs in the early morning sky. Ignore them. The objects are fully identified. They’re the planets Venus and Jupiter – the brightest objects in the night sky after the Moon. They’re crossing paths, as Jupiter pulls away from the Sun as seen from Earth, and Venus drops toward it. Venus is the brighter of the two. Venus and Jupiter could have a big influence on our own planet – not astrologically, but gravitationally. The planets all probably moved around a lot when the solar system was young. Today, their configuration is stable. And it should remain stable for hundreds of millions of years. But it’s impossible to predict beyond that. Tiny differences in a planet’s current orbit could have a big impact on its position in the far distant future. As a planet moves toward or away from the Sun, its gravity pushes and pulls the other planets, changing their location. Earth is most influenced by the gravity of Venus – which passes closer to us than any other world – and Jupiter – the most massive planet. They squeeze and stretch Earth’s orbit over a cycle of about 400,000 years. In the distant future, they could destabilize the orbit – dramatically changing Earth’s place in the solar system. Look for these “influential” planets beginning a couple of hours before sunrise. They remain visible deep into the dawn twilight. Script by Damond Benningfield

Based on how bright the stars look to our eyes alone, Deneb ranks among the 20 brightest stars in the night sky. Because the stars are at different distances, though, that ranking is a little misleading. If we could arrange them based on their true brightness, Deneb would outshine them all. In fact, it might be the brightest of all the stars that are easily visible to the unaided eye. Deneb is high in the east-northeast at nightfall, at the lower left corner of the bright Summer Triangle. Deneb is a blue supergiant – it’s much bigger, heavier, and hotter than the Sun. And it’s much, much brighter. Exactly how much brighter isn’t certain. That’s because there’s disagreement about the star’s distance. Astronomers have measured the distance with several techniques. Some are more direct, while others are based on models of different types of stars. That’s yielded estimates of about 1400 to 2600 light-years. And that makes a big difference. At the greater distance, Deneb would be almost four times brighter than at the smaller one. So Deneb’s true luminosity – the value when you add up all wavelengths of light – is somewhere between 50,000 and 200,000 times the Sun’s. If the high end of that range is correct, then Deneb is one of the brighter stars in the entire galaxy – and perhaps the brightest star that’s easily seen with the eye alone. Script by Damond Benningfield

Altair is a close neighbor – just 16.7 light-years away. Only about 50 star systems are closer. And it’s bigger and brighter than the Sun, so it’s easy to study. Even so, not even the largest individual telescopes can see it as more than a bright dot. Yet astronomers have managed to take a fairly detailed picture of it. They’ve done so with a technique known as interferometry. It combines the views from several fairly small telescopes that are linked together. That reveals as much detail as a single giant telescope. Just how much detail depends on the number and size of the telescopes, and how far apart they’re spaced. The setup doesn’t necessarily see fainter stars and galaxies, but it does see the universe with greater clarity. With conventional telescopes, astronomers had found that Altair spins in a hurry – once every eight hours, versus about 25 days for the Sun. That suggested the star was flattened. They measured that flattening with an interferometer; the star is about 25 percent wider through the equator than through the poles. A few years later, they confirmed that it’s cooler and darker around the equator. And in 2006, they even took a picture of Altair – the first detailed image of any Sun-like star. Altair is high in the southeast at nightfall, at the lower right corner of the bright Summer Triangle. We’ll talk about another member of the triangle tomorrow. Script by Damond Benningfield

A bright Moon is a beautiful sight – unless you have your heart set on seeing the stars. In that case, it’s a pest. The Moon’s glare overpowers many of the stars in the sky. But some manage to shine through even the brightest moonlight. Tonight, for example, even though the Moon is about 95 percent full, three stars are quite easy to find: Vega, Deneb, and Altair – the Summer Triangle. The triangle stands high in the eastern sky at nightfall, and climbs directly overhead later on. Its brightest member is Vega, at the top of the triangle. It’s about 25 light-years away. That means the light you see from the star tonight began its trek across the galaxy in the year 2000. Vega is bigger and heavier than the Sun, and almost 50 times brighter. Deneb is to the lower left of Vega. Its distance is uncertain; more about that tomorrow. What is certain is that it’s a supergiant – many times bigger and more massive than the Sun, and tens of thousands of times brighter. And its fate is pretty well known, too: Deneb is likely to explode as a supernova sometime in the next few million years. Altair is farther to the lower right of Vega. It’s the closest member of the triangle – just 17 light-years away. It’s a lot like Vega, just not quite as impressive. Still, it’s easy to spot through the moonlight – a member of the bright Summer Triangle. Script by Damond Benningfield

The universe follows a set of rules – the laws of physics. Those laws govern everything from the vibrations of the strings on a cello to the motions of the stars and planets. In fact, for centuries it was thought that the stars and planets must produce their own heavenly music – the music of the spheres. The idea was first proposed about 2500 years ago, by Pythagoras of Samos. The Greek philosopher studied the music produced by a lyre – a small, handheld harp. Its tones were produced by the vibrations of the strings. He found a mathematical relationship between the tones and the length of the strings. Since the strings were vibrating, that meant they were moving. Pythagoras then suggested that everything that moves produces its own vibrations – its own music. And that included the heavens. At the time, the leading view of the universe said it consisted of a series of spheres. The Sun, Moon, and known planets were embedded in their own spheres. The stars were in the outer sphere. As the spheres moved, Pythagoras said they should produce musical notes. The relationships between the spheres determined the specific notes. Taken together, they should produce a beautiful cosmic harmony. Over the centuries, some thought the music was real. Others thought of it as more symbolic – an indication that the universe was in harmony – a different way to “hear” the music of the spheres. Script by Damond Benningfield

Many of us have our own muse – someone who’s inspired us in a profound way. Such people can be seen as the descendants of the original Muses – goddesses who inspired great accomplishments in music, dance, poetry – and astronomy. The Muses were the daughters of Zeus, the king of the gods of Olympus, and Mnemosyne, the goddess of memory. And they were the great grand-daughters of Uranus, one of the Titans – the gods who came before the Olympians. The Muse of astronomy was Urania – a name that means “heavenly.” She inspired people to look at the stars, to draw maps of them, and to create stories about them. She was also said to be able to see the future by “reading” the stars. In classical artworks, Urania often is shown looking skyward, and wearing a cloak that’s covered in stars. In some pieces, she also has a halo of stars. Because the stars were important for navigation and mapping in the ancient world, her symbols were a globe and a compass. In the 16th century, Danish astronomer Tycho Brahe named his observatory “Uraniborg” in her honor. A half-dozen other European observatories have also borne her name. And she’s in the official seals of the U.S. Naval Observatory and the Royal Astronomical Society of Canada. So the mythical Muse who inspired people to watch the sky in ancient Greece is still an inspiration today. Script by Damond Benningfield

The number of known “exoplanets” that might sustain life keeps going up – it’s in the hundreds. Such a planet is in the “habitable zone” of its parent star – the distance where conditions are most comfortable for life. That zone depends on the type of star. It’s close in for small, faint stars, but a long way out for stars that are big and bright. In fact, such stars might not even have a habitable zone. And if they do, it won’t last long. One example is Antares, the heart of the scorpion, which huddles close to the Moon tonight. Antares consists of two stars. The star we see is many times bigger and heavier than the Sun. And it’s probably 50,000 to a hundred thousand times brighter than the Sun or more. For a planet to receive the same amount of energy that Earth gets from the Sun, it would have to be at least 225 times farther out than Earth is. And at that distance, the second star in the system might make the planet’s orbit unstable. It might even kick the planet out of the system. Even if a planet did exist in the habitable zone, it wouldn’t last long. Antares is likely to explode in the next million years or so – a bad development for any planet. So if anything inhabits the Antares system, it’s probably just visiting – perhaps some scientists from another star system watching this impressive but unfriendly pair of stars. Script by Damond Benningfield

Mars appears to have a shadow this evening – a faint star with one of the more lyrical names in the heavens: Zavijava. Mars looks like a fairly bright orange star, quite low in the west as darkness falls. Zavijava is almost touching it. It’s a good bit fainter than Mars, though, so you might want to use binoculars to enhance the view. Zavijava is a pretty close neighbor. According to the Gaia space telescope, it’s just 35.88 light-years away. Only a few dozen stars that are visible to the unaided eye are closer. The star’s name comes from an Arabic phrase that means “corner of the barking dog.” But Zavijava isn’t related to any of the dogs in the night sky. Instead, it’s one of the brighter stars of the constellation Virgo, so it’s also known as Beta Virginis. Zavijava is a little bit bigger and heavier than the Sun. It’s younger than the Sun by roughly one-and-a-half billion years. But because of its greater heft, it’s already nearing the end of the main phase of life. Before long – on the astronomical timescale – it’ll undergo a series of changes in its core. That will make the star much bigger and brighter. It will remain in that phase for hundreds of millions of years. Over the past few decades, astronomers have reported the discovery of several possible planets around the star. None of those reports has stood up. But the search continues – for worlds orbiting Zavijava. Script by Damond Benningfield

For a star, passing too close to a black hole is never a good thing. If the star doesn’t get eaten, it can get kicked into a high-speed jaunt across the cosmos. And astronomers can track the path of such a star back to its birthplace. One such high-speed star is plowing through the galaxy at more than a million miles per hour. Today, it appears near the twins of Gemini. But it may have been born halfway across the sky, in Pegasus. When astronomers traced the star’s path, they found that it intersected with the star cluster Messier 15 about 20 million years ago. The star is the same age as the stars in the cluster, and it has the same composition. That suggests the star was born in M15, then booted out – probably by an encounter with a black hole more than a hundred times the mass of the Sun. Other astronomers had reported the possibility of such a black hole more than 20 years ago. And the high-speed star appears to confirm it. Originally, the star would have been a member of a binary. But the two stars passed close to the black hole – closer than Earth is from the Sun. In a complex gravitational dance, the binary was ripped apart. One star was gobbled up by the black hole. But the other one got away – beginning a high-speed dash across the galaxy. Today, the star is more than 37,000 light-years from the cluster – a possible survivor of a close encounter with a black hole. Script by Damond Benningfield

A small star with a planetary companion appears to be making a high-speed exit from the center of the Milky Way – perhaps fast enough to escape the galaxy entirely. The system is more than 24,000 light-years away, in Sagittarius. It appears to contain a red-dwarf star – a cool, faint ember about 20 percent the mass of the Sun. It’s accompanied by a “super-Neptune” – a planet about 30 times the mass of Earth. They’re separated by less than the distance from Earth to the Sun. What makes the system especially interesting is its high speed – at least 1.2 million miles per hour. That’s not fast enough to leave the Milky Way behind. But it could be moving a good bit faster. The system might have started as a member of a binary – two stars bound by gravity. The stars passed too close to the monster black hole in the galaxy’s heart. The black hole grabbed the other star, and gave the escapee a giant kick. On the other hand, the kick could have come from an encounter with a smaller black hole in the Milky Way’s crowded center. How the star maintained its grip on the planet is a key question. But the planet must have been in a tight orbit to avoid being yanked away. Researchers were scheduled to take some follow-up observations this month. That might reveal whether the system really is a star and planet on a high-speed ride through the galaxy. We’ll talk about another possible escapee tomorrow. Script by Damond Benningfield

The supermassive black hole at the heart of the Milky Way is never quiet – it’s constantly popping off. The black hole is more than four million times the mass of the Sun. It grabs passing gas clouds, asteroids, and other objects. It also sponges up gas from the “winds” produced by nearby stars. This forms a swirling disk around the black hole. As material spirals inward, it gets extremely hot. Astronomers watched the black hole with James Webb Space Telescope. They found that it produces several bright outbursts every day, with each one lasting an hour or longer. Between these outbursts there were fainter flares that usually lasted less than a minute. The flares may have different causes. Shorter flares may be caused by turbulence in the disk, which squeezes and heats pockets of gas. Particles bounce around inside these pockets, heating up and producing outbursts of energy. The longer flares may explode when magnetic fields twist together, then snap. That produces big outbursts of particles and energy like the giant flares on the Sun. The astronomers hope to take an even longer look at the system, helping them learn more about the constant flare-ups from the Milky Way’s monster black hole. The black hole is in Sagittarius. The constellation is in the south on summer evenings, and forms the outline of a teapot. The black hole is immersed in the “steam” above the spout – 26,000 light-years away. Script by Damond Benningfield

Sagittarius marks the center of our home galaxy, the Milky Way. So the constellation is packed with stars, star clouds, and star clusters. But one of the clusters doesn’t belong to the Milky Way at all – at least not yet. It’s in a small, puffy galaxy on the far edge of the Milky Way’s disk. Messier 54 is a globular cluster – a ball-shaped region about 150 light-years across, packed with hundreds of thousands of stars. Native globulars are among the Milky Way’s oldest residents – they were born with the galaxy itself. But a few of the clusters were born in other galaxies, then absorbed when their home galaxies were absorbed by the Milky Way. For a long time, astronomers thought that M54 was a charter member of the Milky Way – one of its early globular clusters. A couple of decades ago, though, they found that it’s near the center of a newly discovered galaxy, the Sagittarius Dwarf. That puts it outside the Milky Way’s disk. But the Milky Way is pulling the smaller galaxy in. Eventually, it will incorporate all of the galaxy’s stars. So M54 will become a member of the Milky Way – one of its newest residents – and one of its oldest. Sagittarius scoots low across the south on summer nights. It looks like the outline of a teapot. M54 is at the lower left corner of the teapot, but you need a telescope to see it. Script by Damond Benningfield

Mars won’t exactly roll out the red carpet for human explorers. In fact, the Red Planet could be deadly. It’s bitterly cold, the air is too thin to breathe, there’s no ozone layer to block the Sun’s ultraviolet rays, and there’s no magnetic field to deflect solar storms. And if that’s not enough, there’s one more potential hazard: dust. A recent study said the dust could damage lungs and other organs and cause nasty diseases. Dust covers much of the planet, giving Mars its orange color. It’s easily lofted by the wind, and dust storms can blanket much or all of the planet. Researchers studied the dust, along with problems that Apollo astronauts experienced with Moon dust. They found that the Mars dust grains are too small to be filtered out by the lungs. Instead, they’d enter a person’s bloodstream. Not only are the grains abrasive, but the dust contains high levels of some nasty compounds. So the dust could cause everything from thyroid problems to a condition similar to black-lung disease. Some ailments could be treated on Mars. But any serious problems might require help from Earth – a journey of months. So Mars travelers will need good air filters, self-cleaning spacesuits, and other methods to protect them from the deadly sands of Mars. Mars stands close to the crescent Moon as darkness falls this evening. It looks like a fairly bright star – a hazardous destination for human explorers. Script by Damond Benningfield

Astronomers generally don’t play many official practical jokes. But an Italian astronomer played one more than two centuries ago. And the joke is still there for everyone to see. It’s in Delphinus, the dolphin. The constellation is small and fairly dim. But five of its stars form an outline that really does resemble a dolphin, making it easy to find. It’s a third of the way up the eastern sky at nightfall, with the dolphin’s tail on the right and its snout on the left. The brightest members of the outline are Beta and Alpha Delphini. Beta is a binary – two stars bound by their mutual gravitational pull. Both are bigger, brighter, and heavier than the Sun. Alpha consists of three stars. All of them are more impressive than the Sun, with the main star almost four times the mass of the Sun. The stars also have proper names. Beta is known as Rotanev; Alpha is called Sualocin. And that’s where the joke comes in. The names first appeared in 1814, in an atlas published by the director of the Palermo Observatory. The names caught on, but their origin was a mystery. It was solved by a British astronomer 45 years later. He realized that the observatory’s assistant director at the time was Niccolo Cacciatori. In English, the name would be Nicholas Hunter; in Latin, Nicolaus Venator. Spell the Latin names backwards, and you come up with Sualocin and Rotanev – a little joke among the stars of the dolphin. Script by Damond Benningfield

Zeta Tauri is the kind of star that few of us really notice. It’s at the tip of one of the horns of Taurus, the bull. But it shines at only third magnitude. That’s no problem under dark skies, but tough to see from a light-polluted city. It’ll be much easier to find before dawn tomorrow, though, because it’ll stand just a whisker from Venus, the brilliant “morning star.” Zeta Tauri is actually two stars, not one. They’re separated by a bit more than the distance from Earth to the Sun. But at the system’s distance of about 440 light-years from Earth, it’s impossible to see them as individual stars, even with the largest of telescopes. In fact, it’s tough to even learn the nature of the two stars. One of the stars is easy to figure out. It’s about 11 times the mass of the Sun, five times wider than the Sun, and thousands of times brighter. But its companion isn’t fully understood. It may be a white dwarf – a stellar corpse as heavy as the Sun. The main star is blowing a strong wind of gas into space. That’s formed a cloud around the star. The white dwarf may pull in some of that material. As it piles up on the white dwarf it gets much hotter, making the system a strong source of X-rays. In the next few million years, the heavier star of Zeta Tauri is likely to explode as a supernova. That’ll make it impossible to overlook this currently meager star. Script by Damond Benningfield

Water, water everywhere, nor any drop to drink. The line from “The Rime of the Ancient Mariner” is true not only on Earth, but across the solar system. Water is everywhere. But it’s not in a form you could drink. It’s in the clouds of the giant outer planets, frozen in the surfaces and ice caps of planets and moons, or buried far below their surfaces. One example is Pluto. The dwarf planet is billions of miles from the Sun, so its surface is frozen. But there’s evidence that liquid water lurks far below. In fact, there could be a global ocean up to a hundred miles deep. One bit of evidence is a feature called Sputnik Planitia – a fairly smooth plain about 600 miles across. It’s almost pure white. And there are no impact craters, suggesting that the surface is young. Among its features are floating blocks of frozen gases. They resemble slabs of ice in the polar regions of Earth. That suggests they could be floating atop liquid water. Plumes of water flow upward, freezing and pushing older ice outward. In fact, the feature might have formed when a big asteroid slammed into Pluto. It vaporized the surface, exposing the ocean below. The water quickly froze, forming the plain we see today. Pluto lines up opposite the Sun this week. It’s in view all night, and shines brightest for the whole year. Script by Damond Benningfield